Bump ORCA version to 2.48.6
Bump ORCA version to 2.48.6

Commit 7a60859 was pushed without a version bump. Ideally, README
commits do not need a version bump and instead `ci-skip` tag should be
used in the commit message.

However this version bump is now necessary to make ORCA CI happy.
Currently check_existing_tag job is red since we missed version
bump/ci-skip tag in the previous commit.

Signed-off-by: Ekta Khanna <2fbdcb8e3470ad1f53bbeb24e2deced604b8cfa5@pivotal.io>

greenplum-db/gpdb,jmcatamney/gpdb,lisakowen/gpdb,jmcatamney/gpdb,adam8157/gpdb,lisakowen/gpdb,lisakowen/gpdb,jmcatamney/gpdb,50wu/gpdb,greenplum-db/gporca,greenplum-db/gporca,greenplum-db/gporca,lisakowen/gpdb,adam8157/gpdb,greenplum-db/gpdb,lisakowen/gpdb,jmcatamney/gpdb,greenplum-db/gpdb,jmcatamney/gpdb,50wu/gpdb,xinzweb/gpdb,50wu/gpdb,greenplum-db/gpdb,greenplum-db/gporca,xinzweb/gpdb,adam8157/gpdb,adam8157/gpdb,xinzweb/gpdb,greenplum-db/gpdb,50wu/gpdb,lisakowen/gpdb,greenplum-db/gpdb,adam8157/gpdb,50wu/gpdb,greenplum-db/gpdb,xinzweb/gpdb,50wu/gpdb,lisakowen/gpdb,jmcatamney/gpdb,jmcatamney/gpdb,50wu/gpdb,jmcatamney/gpdb,greenplum-db/gpdb,adam8157/gpdb,adam8157/gpdb,adam8157/gpdb,xinzweb/gpdb,xinzweb/gpdb,xinzweb/gpdb,50wu/gpdb,lisakowen/gpdb,xinzweb/gpdb